The science and practice of orthodontia involve the reorienting or moving of teeth from one position to another not only to improve aesthetic appearance but also to improve the functioning of the teeth for their purposes of chewing food and maintaining a healthy mouth area. It is conventional to move the teeth by metallic bands around the teeth in combination with an arch wire and elastomeric members for applying various forces to the bands. The bands, elastomers and wire are interconnected by brackets rigidly mounted on the periphery of the bands.
Teeth are not rigidly held in the jaw bone but are capable of rotational and linear movement without damage to either the teeth or the jaw and without causing the teeth to be unduly loosened. This semi-fluid nature of the jawbone and the way teeth are attached thereto are the physical characteristics controlling the practice of orthodontia.
Some recent techniques involve the cementing of a bracket directly to the surface of the tooth. Thereafter, an arch wire, usually of a square or rectangular cross-section, is utilized in the conventional manner. It is lock-wired to the brackets by means of a thin ligature wire. When it is desired to move a tooth in a linear direction along the jaw, rubber bands or the like are adjusted to produce a force in the desired direction. The arch wire may be used for raising, lowering or rotating the tooth. The tooth being in a semi-free floating condition then begins to move in response to the forces applied. Problems arise because the force of linear translation is of necessity applied at the surface of the tooth thereby producing not only a linearly translating force but also a moment around the center of rotation of the tooth. Numerous methods have been utilized to avoid the undesirable rotation of a tooth as it is linearly translated including (1) anticipatory pre-rotation of a tooth in the opposite direction in order to have it arrive at its ultimate destination at a correct orientation and (2) post arrival corrective rotation.
In current aperture bounded on three sides by the bracket and on the fourth by the tooth to which it is attached. Said aperture may extend the full vertical length of the bracket in substantially the same direction as the tooth, that is, running from the root toward the crown. The aperture is of significance in two aspects of the invention described herein, one aspect being the tooth rotation problem described above and the second aspect being a means for attaching additional orthodontic bracketry to a tooth on which the apertured bracket is mounted.
Various additonal orthodontic bracketry may be mounted on the aperture bracket by means of pin like projections extending into said aperture; U.S. Pat. No. 4,310,306 to Wallshein is illustrative.
It is conventional to lock-wire the additional bracketry to the tooth brackets by using additional ligature wire to prevent inadvertent dislodgement during the orthodontic procedure or as the patient goes through his normal daily regiment.